Basketball player Jason Collins has come out as gay, becoming the first active male athlete in any of the four major American professional sports to do so.

The 34-year-old centre, who has played 12 seasons in the NBA, made the announcement in a first-person account posted on Sports Illustrated's website.

He wrote: "If I had my way, someone else would have already done this. Nobody has, which is why I'm raising my hand."

Collins played for the Wizards this past season

Collins' disclosure prompted support from all corners, including from White House spokesman Jay Carney, who called the NBA player's decision courageous.

Mr Carney said: "We view that as another example of the progress that has been made and the evolution that has been taking place in this country."

Former President Bill Clinton also voiced encouragement for Collins, asking fans, NBA colleagues and the media to support and respect him in a statement.

Mr Clinton has known Collins since the athlete attended Stanford University with his daughter, Chelsea.

The former first daughter also joined those offering support on social media.

She tweeted: "Very proud of my friend Jason Collins for having the strength and courage to be the first openly gay player in the NBA."

Several male athletes have previously come out after they retired, including the NBA's John Amaechi, the NFL's Esera Tuaolo and Major League Baseball's Billy Bean. But Collins is the first to do so while planning to continue playing.

NBA Commissioner David Stern said in a statement: "Jason has been a widely respected player and teammate throughout his career and we are proud he has assumed the leadership mantle on this very important issue."

Collins has played for six teams during his professional career, finishing his latest season with the Washington Wizards. The free agent says he wants to keep playing.

Collins played in a Final Four for Stanford and reached two NBA Finals. His twin brother, Jarron, was also a longtime NBA centre.

Mostly a back-up in his career, Collins has played for the Nets, Grizzlies, Timberwolves, Hawks, Celtics and Wizards. He was traded from Boston to Washington in February. Collins was the 18th pick in the first round of the 2001 NBA Draft.

Many female athletes have come out while actively participating in various sports, including basketball, soccer and golf. Tennis star Martina Navratilova was among the first.